Surgical tools to facilitate delivery of a neurostimulator into the pterygopalatine fossa

ABSTRACT

A surgical tool configured to facilitate delivery of a neurostimulator to a craniofacial region of a subject includes a handle portion, an elongate shaft having a contoured distal portion, and an insertion groove on the elongate shaft. The elongate shaft is configured to be advanced under a zygomatic bone along a maxillary tuberosity towards a pterygopalatine fossa. The distal portion includes a distal dissecting tip. The insertion groove is configured to receive, support, and guide a medical device or instrument.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/688,300, filed Jan. 15, 2010, which claims priority to U.S.Provisional Patent Application Ser. No. 61/145,122, filed Jan. 16, 2009(Now Expired). This application incorporates the above-identifiedapplications herein by reference in their entirety and claims priorityto all aforementioned applications for all purposes.

TECHNICAL FIELD

The present disclosure relates generally to surgical tools configured tofacilitate delivery of medical devices to a craniofacial region of asubject, and more particularly to surgical tools configured tofacilitate delivery of an implantable neurostimulator to apterygopalatine fossa of a subject.

BACKGROUND OF THE INVENTION

Electrical stimulation of peripheral and central neural structures hasshown increased interest due to the potential benefits it may provide toindividuals suffering from many neurological and behavioral diseases.Many of these therapies today are not well accepted due to the invasivenature of the therapy, even though the efficacy is quite good. This hascreated a need for less invasive therapies that are directed towardpatient and physician clinical needs.

Headaches are one of the most debilitating ailments that afflictmillions of individuals worldwide. The specific pathophysiology ofheadaches is unknown. Known sources of headache pain consist of trauma,vascular, autoimmune, degenerative, infectious, drug andmedication-induced, inflammatory, neoplastic, metabolic-endocrine,iatrogenic, musculoskeletal and myofacial causes. Also, even though thepossible underlying cause of the headache pain is identified andtreated, the headache pain may persist.

Currently, the sphenopalatine (pterygopalatine) ganglion (SPG) is atarget of manipulation in clinical medicine to treat headaches. The SPGis an extracranial neuronal center located behind the nose. It consistsof parasympathetic neurons that innervate (in part) the middle cerebraland anterior cerebral blood vessels, the facial blood vessels, and thelacrimal glands. The SPG also consists of sympathetic and sensory nervefibers that pass through the SPG in route to their end organs.Manipulation of the SPG is mostly performed in attempted treatments ofsevere headaches, such as cluster headaches or chronic migraines.

Various clinical approaches have been used for over 100 years tomodulate the function of the SPG to treat headaches. These proceduresvary from least invasive (e.g., transnasal anesthetic blocks) to muchmore invasive (e.g., surgical ganglionectomy), as well as procedures,such as surgical anesthetic injections, ablations, gamma knife andcryogenic surgery. These later procedures are very invasive, and mostare non-reversible. In both cases, the surgical approach is typicallythrough the nostrils or the greater palatine foramen.

SUMMARY OF THE INVENTION

According to another aspect of the present disclosure, a surgical toolconfigured to provide surgical access to a craniofacial region of asubject includes a handle portion, an elongate shaft having a contoureddistal portion, and an insertion groove on the elongate shaft. Thedistal portion is shaped and configured to maintain contact with aposterior maxilla and elevate a periosteum off of the posterior maxillato avoid soft tissue dissection. The distal portion includes a distaldissecting tip. The insertion groove is configured to receive atunneling member.

According to another aspect of the present disclosure, a surgical toolconfigured to deliver a neurostimulator to a craniofacial region of asubject includes a handle portion, an elongate shaft having a contoureddistal portion, and an insertion groove on the elongate shaft. Theelongate shaft is configured to be advanced under a zygomatic bone alonga maxillary tuberosity towards a PPF. The distal portion includes adistal dissecting tip. The insertion groove is configured to deploy theneurostimulator.

According to another aspect of the present disclosure, a method isprovided for delivering a neurostimulator to within close proximity of asphenopalatine ganglion (SPG). One step of the method includes making anincision at a gingival-buccal insertion site. A first surgical tool isthen inserted into the incision. Next, the first surgical tool isadvanced under a zygomatic bone along a maxillary tuberosity towards PPFto form a first surgical access cavity. A second surgical access cavityis then formed at an end of the first surgical access site that is inclose proximity to the SPG. The neurostimulator is delivered in closeproximity to the SPG via the first and second surgical access cavities.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomeapparent to those skilled in the art to which the present disclosurerelates upon reading the following description with reference to theaccompanying drawings, in which:

FIG. 1 is a perspective view showing part of the nervous innervation ofthe anterior craniofacial skeleton;

FIG. 2A is a perspective view of a surgical tool configured to providesurgical access to a craniofacial region of a subject constructed inaccordance with one aspect of the present disclosure;

FIG. 2B is a top view of the surgical tool in FIG. 2A;

FIG. 3 is a schematic illustration showing a distal portion of thesurgical tool in FIGS. 2A-B inserted into a craniofacial region of asubject;

FIG. 4A is a side view of the surgical tool in FIGS. 2A-B (handleomitted for clarity);

FIG. 4B is a side view of the surgical tool in FIG. 4A with a handle;

FIG. 4C is a cross-sectional view taken along Line 4C-4C in FIG. 2B;

FIG. 5 is an image showing an alternative configuration of the distalportion in FIGS. 2A-B;

FIG. 6A is a perspective view showing an alternative configuration ofthe insertion groove in FIGS. 2A-B;

FIG. 6B is a cross-sectional view taken along Line 6B-6B in FIG. 6A;

FIG. 7A is a perspective view showing another alternative configurationof the insertion groove in FIGS. 2A-B;

FIG. 7B is a cross-sectional view taken along Line 7B-7B in FIG. 7A;

FIG. 8 is a magnified perspective view showing the distal portion of thesurgical tool in FIGS. 2A-B;

FIG. 9 is a magnified side view of the distal portion in FIG. 8;

FIG. 10 is a perspective view of a surgical tool configured to deliver aneurostimulator to a craniofacial region of a subject constructed inaccordance with another aspect of the present disclosure;

FIG. 11 is a perspective view of a neurostimulator that can be deliveredto a craniofacial region of a subject using the surgical tool in FIG.10;

FIG. 12 is a schematic illustration showing a neurostimulator deliveryapparatus;

FIG. 13 is a side view of the surgical tool in FIG. 10 (handle omittedfor clarity);

FIG. 14 is a top view of the surgical tool in FIG. 10;

FIG. 15 is a magnified perspective view showing the distal portion ofthe surgical tool in FIG. 14;

FIG. 16 is a magnified perspective view showing a distal dissecting tipof the surgical tool in FIG. 10;

FIG. 17 is a cross-sectional view taken along Line 17-17 in FIG. 13;

FIG. 18 is a process flow diagram illustrating a method for delivering aneurostimulator to within close proximity of a sphenopalatine ganglion(SPG) according to another aspect of the present disclosure;

FIG. 19 is a perspective view of the anterior craniofacial skeletonshowing a gingival-buccal insertion site;

FIG. 20 is a perspective view showing the surgical tool of FIGS. 2A-Bbeing inserted into the gingival-buccal insertion site;

FIG. 21 is a perspective view showing the distal dissecting tip of thesurgical tool in FIG. 20 engaging the junction formed by the posteriormaxillary buttress and the pterygoid plate;

FIG. 22 is a perspective view showing a surgical access cavity formed bythe surgical tool in FIG. 21;

FIG. 23 is a perspective view showing a tunneling member being matedwith an insertion groove of the surgical tool in FIG. 14;

FIG. 24 is a perspective view showing the surgical tool in FIG. 23following withdrawal of the tunneling member; and

FIG. 25 is a schematic illustration showing a neurostimulator deliveryapparatus being used to load a neurostimulator (FIG. 11) onto thesurgical tool in FIG. 24.

DETAILED DESCRIPTION

The present disclosure relates generally to surgical tools configured tofacilitate delivery of medical devices to a craniofacial region of asubject, and more particularly to surgical tools configured tofacilitate delivery of an implantable neurostimulator to apterygopalatine fossa (PPF) of a subject. Surgical tools of the presentdisclosure generally comprise a handle portion, an elongate shaft thatincludes a distal dissecting tip and is configured to be advanced undera zygomatic bone along a maxillary tuberosity towards a PPF, and aninsertion groove on the elongated shaft that is configured to receive,support, and guide a medical device or instrument. As discussed ingreater detail below, the present disclosure may be employed to assistin treating a variety of chronic or acute medical conditions. Examplesof such medical conditions can include, but are not limited to, pain(e.g., headache and/or facial pain), movement disorders, epilepsy,cerebrovascular diseases, autoimmune diseases, sleep disorders,autonomic disorders, neurological disorders, urinary bladder disorders,abnormal metabolic states, disorders of the muscular system, andneuropsychiatric disorders.

Unless otherwise defined, all technical terms used herein have the samemeaning as commonly understood by one of ordinary skill in the art towhich the present disclosure pertains.

In the context of the present disclosure, the term “headache” can referto migraines, tension headaches, cluster headaches, trigeminalneuralgia, secondary headaches, tension-type headaches, chronic andepsisodic headaches, medication overuse/rebound headaches, chronicparoxysmal hemicrinia headaches, hemicranias continua headaches,post-traumatic headaches, post-herpetic headaches, vascular headaches,reflex sympathetic dystrophy-related headaches, cervicalgia headaches,caroidynia headaches, sciatica headaches, trigeminal headaches,occipital headaches, maxillary headaches, chary headaches,paratrigeminal headaches, petrosal headaches, Sluder's headache, vidianheadaches, low cerebrospinal fluid pressure headaches, temporomandibularjoint (TMJ) headaches, causalgia headaches, myofascial headaches, allprimary headaches (e.g., primary stabbing headache, primary coughheadache, primary exertional headache, primary headache associated withsexual activity, hypnic headache, and new daily persistent headache),all trigeminal autonomic cephalagias (e.g., episodic paroxysmalhemicranias, short-lasting unilateral neuralgiform headache attacks withconjunctival injection and tearing (SUNCT) and short-lasting unilateralneuralgiform headache attacks with cranial autonomic symptoms (SUNA)),chronic daily headaches, occipital neuralgia, atypical facial pain,neuropathic trigeminal pain, and miscellaneous-type headaches.

As used herein, the term “cluster headache” can refer to extremelypainful and debilitating headaches that occur in groups or clusters.Cluster headaches can include chronic or episodic cluster headaches,cluster-type headaches, histamine headaches, histamine cephalalgia,Raedar's syndrome and sphenopalatine neuralgia.

As used herein, the term “migraine” can refer to an intense anddisabling chronic or episodic headache typically characterized by severepain in one or both sides of the head. Migraines can include, but arenot limited to, migraine without aura, migraine with aura, migraine withaura but without headache, menstrual migraines, variant migraines,transformed migraines, menstrual migraines, complicated migraines,hemiplegic migraines, atypical migraines, chronic migraines,basilar-type migraines, childhood periodic syndromes that are commonlyprecursors of migraine (e.g., abdominal, cyclic vomiting, BPV, etc.),status migrainous, and all types of probable migraines.

As used herein, the term “facial pain” can refer to direct pain thattypically involves nerves supplying the face or, alternatively, indirect(referred) pain from other structures in the head, e.g., blood vessels.The pain may be related to headache (e.g., migraine), muscular syndromes(e.g., TMJ), and herpetic or rheumatic disease or injury.

As used herein, the terms “modulate” or “modulating” can refer tocausing a change in neuronal activity, chemistry and/or metabolism. Thechange can refer to an increase, decrease, or even a change in a patternof neuronal activity. The terms may refer to either excitatory orinhibitory stimulation, or a combination thereof, and may be at leastelectrical, biological, magnetic, optical or chemical, or a combinationof two or more of these. The terms can also be used to refer to amasking, altering, overriding, or restoring of neuronal activity.

As used herein, the term “subject” can refer to any warm-bloodedorganism including, but not limited to, human beings, pigs, rats, mice,dogs, goats, sheep, horses, monkeys, apes, rabbits, cattle, etc.

As used herein, the term “prevent” shall have its plain and ordinarymeaning to one skilled in the art of pharmaceutical or medical sciences.For example, “prevent” can mean to stop or hinder a medical condition,such as a headache.

As used herein, the terms “treat” or “treating” shall have their plainand ordinary meaning to one skilled in the art of pharmaceutical ormedical sciences. For example, “treat” or “treating” can mean to preventor reduce a medical condition, such as a headache.

As used herein, the term “medical condition” can refer to pain, movementdisorders, epilepsy, cerebrovascular diseases, autoimmune diseases,sleep disorders, autonomic disorders, urinary bladder disorders,abnormal metabolic states, disorders of the muscular system, infectiousand parasitic diseases (as provided in ICD-9 codes 1-139), neoplasms (asprovided in ICD-9 codes 140-239), endocrine diseases, nutritional andmetabolic diseases, immunological diseases (as provided in ICD-9 codes240-279), diseases of the blood and blood-forming organs (as provided inICD-9 codes 280-289), mental disorders (as provided in ICD-9 codes290-319), diseases of the nervous system (as provided in ICD-9 codes320-359), diseases of the sense organs (as provided in ICD-9 codes360-389), diseases of the circulatory system (as provided in ICD-9 codes390-459), diseases of the respiratory system (as provided in ICD-9 codes460-519), diseases of the digestive system (as provided in ICD-9 codes520-579), diseases of the genitourinary system (as provided in ICD-9codes 580-629), diseases of the skin and subcutaneous tissue (asprovided in ICD-9 codes 680-709), diseases of the musculoskeletal systemand connective tissue (as provided in ICD-9 codes 710-739), congenitalanomalies (as provided in ICD-9 codes 740-759), certain conditionsoriginating in the perinatal period (as provided in ICD-9 codes760-779), and symptoms, signs, and ill-defined conditions (as providedin ICD-9 codes 780-799).

Pain treatable by the present disclosure can be caused by conditionsincluding, but not limited to, migraine headaches, including migraineheadaches with aura, migraine headaches without aura, menstrualmigraines, migraine variants, atypical migraines, complicated migraines,hemiplegic migraines, transformed migraines, and chronic dailymigraines, episodic tension headaches, chronic tension headaches,analgesic rebound headaches, episodic cluster headaches, chronic clusterheadaches, cluster variants, chronic paroxysmal hemicranias, hemicraniacontinua, post-traumatic headache, post-traumatic neck pain,post-herpetic neuralgia involving the head or face, pain from spinefracture secondary to osteoporosis, arthritis pain in the spine,headache related to cerebrovascular disease and stroke, headache due toa vascular disorder, reflex sympathetic dystrophy, cervicalgia (whichmay be due to various causes including, but not limited to, muscular,discogenic or degenerative, including arthritic, posturally related ormetastatic), glossodynia, carotidynia, cricoidynia, otalgia due tomiddle ear lesion, gastric pain, sciatica, maxillary neuralgia,laryngeal pain, myalgia of neck muscles, trigeminal neuralgia (sometimesalso termed tic douloureux), post-lumbar puncture headache, lowcerebro-spinal fluid pressure headache, TMJ joint disorder, atypicalfacial pain, ciliary neuralgia, paratrigeminal neuralgia (sometimes alsotermed Raeder's syndrome), petrosal neuralgia, Eagle's syndrome,idiopathic intracranial hypertension, orofacial pain, myofascial painsyndrome involving the head, neck and shoulder, chronic migraneousneuralgia, cervical headache, paratrigeminal paralysis, sphenopalatineganglion (SPG) neuralgia (sometimes also termed lower-half headache,lower facial neuralgia syndrome, Sluder's neuralgia and Sluder'ssyndrome), carotidynia, vidian neuralgia, causalgia, atypicalodontalgia, cluster tic syndrome, geniculate neuralgia, glossopharyngealneuralgia, occipital neuralgia, temporal arteritis, and/or a combinationof the above.

Movement disorders treatable by the present disclosure may be caused byconditions including, but not limited to, Parkinson's disease,cerebropalsy, dystonia, essential tremor and hemifacial spasms.

Epilepsy treatable by the present disclosure may be, for example,generalized or partial.

Cerebrovascular disease treatable by the present disclosure may becaused by conditions including, but not limited to, aneurysms, strokes,and cerebral hemorrhage.

Autoimmune diseases treatable by the present disclosure include, but arenot limited to, multiple sclerosis.

Sleep disorders treatable by the present disclosure may be caused byconditions including, but not limited to, circadian rhythm disorders,sleep apnea and parasomnias.

Autonomic disorders treatable by the present disclosure may be caused byconditions including, but not limited to, gastrointestinal disorders,including but not limited to gastrointestinal motility disorders,nausea, vomiting, diarrhea, chronic hiccups, gastroesphageal refluxdisease, and hypersecretion of gastric acid, autonomic insufficiency,autonomic instability, excessive epiphoresis, excessive rhinorrhea, andcardiovascular disorders including, but not limited, to cardiacdysrythmias and arrythmias, hypertension, carotid sinus disease,Holmes-Adie syndrome, orthostatic hypotension, striatonigraldegeneration, vasovagal syncope, Lyme disease and autonomic instability.

Neurological disorders treatable by the present disclosure may be causedby conditions including, but not limited to, hemifacial spasm,Melkersson-Rosenthal syndrome, and Parry-Romberg syndrome.

Urinary bladder disorders treatable by the present disclosure may becaused by conditions including, but not limited to, spastic or flaccidbladder.

Abnormal metabolic states treatable by the present disclosure may becaused by conditions including, but not limited to, hyperthyroidism orhypothyroidism.

Disorders of the muscular system treatable by the present disclosure caninclude, but are not limited to, muscular dystrophy, and spasms of theupper respiratory tract and face.

Neuropsychiatric or mental disorders treatable by the present disclosuremay be caused by conditions including, but not limited to, depression,schizophrenia, bipolar disorder, and obsessive-compulsive disorder.

A brief discussion of the pertinent anatomy and neurophysiology isprovided to assist the reader with understanding the present disclosure.The autonomic nervous system innervates numerous pathways within thehuman body and consists of two divisions: the sympathetic and theparasympathetic nervous systems. The sympathetic and parasympatheticnervous systems are antagonistic in their action, balancing the othersystem's effects within the body. The sympathetic nervous system (SNS)usually initiates activity within the body, preparing the body foraction, while the parasympathetic nervous system (PNS) primarilycounteracts the effects of the SNS.

The sphenopalatine ganglia 10 are located on both sides of the head(FIG. 1). It shall be assumed for the following discussion of thepresent disclosure that reference is being made to the SPG 10 located onthe left side of the head. The SPG 10 is located behind the posteriormaxilla 12 in the PPF 14, posterior to the middle nasal turbinate (notshown in detail). The SPG 10 is part of the parasympathetic division ofthe autonomic nervous system; however, the SPG has both sympathetic andparasympathetic nerve fibers, as well as sensory and motor nerve fiberseither synapsing within the ganglion (e.g., parasympathetic) or fibersthat are passing through the ganglion and not synapsing (e.g.,sympathetic, sensory and motor).

The parasympathetic activity of the SPG 10 is mediated through thegreater petrosal nerve (not shown), while the sympathetic activity ofthe SPG is mediated through the deep petrosal nerve (not shown), whichis essentially an extension of the cervical sympathetic chain (notshown). Sensory sensations generated by or transmitted through the SPG10 include, but are not limited to, sensations to the upper teeth,feelings of foreign bodies in the throat, and persistent itching of theear. The SPG 10 transmits sensory information, including pain, to thetrigeminal system via the maxillary division and ophthalmic division(not shown).

One aspect of the present disclosure includes a surgical tool 16 (FIGS.2A-B) configured to provide surgical access to a craniofacial region ofa subject. The surgical tool 16 comprises a handle portion 18, anelongate shaft 20 that includes a contoured distal portion 22 having aflared distal dissecting tip 24, and an insertion groove 26 on theelongate shaft. The surgical tool 16 (FIG. 3) is designed and configuredto be inserted trans-orally from an incision located on the anteriormaxilla 28. Advantageously, the distal portion 22 of the elongate shaft20 is shaped and configured to maintain contact with a posterior maxilla12 and elevate a periosteum off of the posterior maxilla to avoid softtissue dissection. Consequently, the contoured design of the distalportion 22 can prevent unwanted soft tissue injury or bleeding duringuse of the surgical tool 16.

As shown in FIG. 4A, the surgical tool 16 comprises a proximal portion30, a contoured distal portion 22, and an intermediate portion 32extending between the proximal portion and the distal portion. Theproximal portion 30 and the intermediate portion 32 define alongitudinal plane P that extends between the proximal and intermediateportions. The surgical tool 16 can have a length L of about 10 cm toabout 30 cm. For example, the surgical tool 16 can have a length L ofabout 12 cm (e.g., 12.4 cm). The surgical tool 16 can be made of a rigidor semi-rigid medical grade metal or metal alloy, such as titanium orstainless steel, medical grade plastics (e.g., PEEK, polycarbonate,nylon), ceramics (e.g., aluminum, zirconium oxide), glass, combinationsof metals, ceramics, plastics or plastic composites, and the like.

The proximal portion 30 of the surgical tool 16 can have a thicknessT_(p) of about 0.5 mm to about 8 mm, such as about 2 mm to about 4 mm(e.g., about 3 mm). The intermediate portion 32 can have a thicknessthat is similar or identical to the thickness T_(p) of the proximalportion 30. It will be appreciated, however, that the thickness of theintermediate portion 32 can decrease as the intermediate portion tapersto the distal portion 22. As shown in FIG. 4B, the proximal portion 30includes an ergonomic handle 34 that collectively forms the handleportion 18 and is securely disposed thereon. The handle 34 can have alength of about 6 cm to about 12 cm, and vary in diameter from aproximal end 36 (e.g., about 0.5 cm to about 3 cm) to a distal end 8(e.g., about 0.5 cm to about 2 cm). The handle 34 can include variousfeatures to provide grip and tactile maneuverability, such ascircumferential ridges or a cross-hatched precut pattern into thematerial forming the handle. The handle 34 can be made of a rigid orsemi-rigid medical grade metal or metal alloy, such as stainless steel,medical grade plastics, polymers, and the like.

The distal portion 22 of the surgical tool 16 is shaped and configuredto allow a user to simply and accurately traverse the anteriorcraniofacial skeletal anatomy to reach the PPF 14. The distal portion 22is defined by oppositely disposed first and second major surfaces 40 and42, which collectively form an arcuate shape relative to thelongitudinal plane P. For example, the first major surface 40 of thedistal portion 22 has a concave shape relative to the longitudinal planeP. An alternative configuration of the surgical tool 16 is shown in FIG.5. In FIG. 5, the first major surface 40 can be vertically offsetrelative to the longitudinal plane P (e.g., by about 10° to about 90°)so that the distal portion 22 has a partly twisted or helicalconfiguration.

The distal portion 22 (FIGS. 4A-B) can have a thickness T_(d) of about 2mm to about 5 mm. The thickness T_(d) of the distal portion 22 can beuniform or, alternatively, the thickness T_(d) can decrease or taper atthe distal dissecting tip 24. The distal portion 22 can have a radius ofcurvature so that a user can maintain contact with the posterior maxilla12 while advancing the surgical tool 16 to the PPF 14. For example, thedistal portion 22 can have a radius of curvature of about 8 cm to about3 cm. Additionally, at least a portion of the distal dissecting tip 24can be collinear with the longitudinal plane P.

The surgical tool 16 (FIGS. 2A-B) additionally includes an insertiongroove 26 on the elongate shaft 20 and, in particular, on the distalportion 22. The insertion groove 26 is adapted, shaped, and configuredto receive, support, and guide a tunneling member 44 (FIG. 22), such anelectrode lead blank. The tunneling member 44 (e.g., an electrode leadblank) can include any device that has approximately the same diameterof an electrode lead and is configured as a blunt dissector to create apath for the electrode lead. As shown in FIGS. 2A-B, the insertiongroove 26 extends across the distal portion 22 of the surgical tool 16between the distal dissecting tip 24 and the intermediate portion 32.For example, the insertion groove 26 can extend across only the distalportion 22 of the surgical tool 16 and not the intermediate portion 32and/or the proximal portion 30.

The insertion groove 26 can be embedded or recessed in the first majorsurface 40 of the distal portion 22. The insertion groove 26 is recessedin the first major surface at angle A_(g). The angle A_(g) is formedbetween a radial plane RP that extends between opposing edges 148 and150 of the distal portion 22, and a plane P_(g) that extends transverseto the length L_(g) of the insertion groove 26. As shown in FIG. 4C, theangle A_(g) can be about 90°. Alternatively, the angle A_(g) can beabout 45° (FIGS. 6A-B). In another example, the angle A_(g) can be lessthan about 10° (e.g., 0°) where the insertion groove 26 extends along anopposing edge 148 of the distal portion 22 (FIGS. 7A-B). It will beappreciated that the configurations of the surgical tool 16 shown inFIGS. 6A-B and FIGS. 7A-B may or may not include a flared distaldissecting tip 24 (as described below).

The particular dimensions of the insertion groove 26 can vary dependingupon the dimensions of surgical guide 16 and/or the dimensions of thetunneling member 44 (FIG. 22). In one example of the present disclosure,all or only a portion of the insertion groove 26 can have a depth ofbetween about 0.5 mm and about 1.2 mm, a width W_(g) (FIG. 8) of betweenabout 1 mm and about 2 mm (e.g., 1.6 mm), and a length L_(g) (FIG. 2B)of between about 2 cm and about 8 cm (e.g., 6 cm). The insertion groove26 can have a semi-circular cross-sectional shape, for example, or anyother cross-sectional shape (e.g., square-shaped, V-shaped, etc.) tofacilitate engagement of the surgical tool 16 with the tunneling member44.

The depth and width W_(g) of the insertion groove 26 can vary across thelength L_(g) of the insertion groove to facilitate engagement andrelease of the tunneling member 44 from the surgical tool 16. Forexample, the depth of the insertion groove 26 tapers from a distal end46 of the insertion groove to a proximal end 48 of the insertion groove.More particularly, the proximal end 48 of the insertion groove 26includes a first depth that is greater than a second depth at the distalend 46 of the insertion groove. As shown in FIG. 8, the depth of theinsertion groove 26 at a proximal end 50 of the distal dissecting tip 24gradually decreases towards a distal end 52 of the distal dissecting tipuntil the insertion groove becomes flush with a first surface 54 of thedistal dissecting tip.

The width W_(g) of the insertion groove 26 also tapers from the proximalend 48 to the distal end 46. As shown in FIG. 8, the width W_(g) of theinsertion groove 26 at the proximal end 50 of the distal dissecting tip24 gradually decreases towards the distal end 52 of the distaldissecting tip until the insertion groove becomes flush with the firstsurface 54 of the distal dissecting tip. The varying depth and widthW_(g) of the insertion groove 26 facilitates engagement and accuratecontrol of the tunneling member 44 during operation of the surgical tool16.

The distal portion 22 of the surgical tool 16 can include a flareddistal dissecting tip 24. By “flared” it is meant that all or only aportion of the distal dissecting tip 24 is shaped and configured toextend away from the distal portion 22 of the elongated shaft 20 axiallyand/or distally, and typically also radially. The distal dissecting tip24 includes a length L_(t) that extends between a proximal end 50 and adistal end 52 thereof. The length L_(t) can be about 0.1 cm to about 1cm, such as about 0.1 cm to about 0.5 cm (e.g., 0.25 cm). The distaldissecting tip 24 also includes a width W_(t) that increases from theproximal end 50 to the distal end 52 of the tip. The width W_(t) of thedistal dissecting tip 24 is greater than the width W_(d) of the distalportion 22. In one example of the present disclosure, the width W_(t) atthe distal end 52 of the distal dissecting tip 24 can be about 2.5 mm toabout 6 mm (e.g., 4.16 mm).

As shown in FIG. 9, the first surface 54 of the distal dissecting tip 24extends at an offset angle A relative to the first major surface 40 ofthe distal portion 22. For example, all or only a portion of the distaldissecting tip 24 can have an increased curvature in the same plane asthe distal portion curvature of the surgical tool 16. The offset angle Acan be less than 180°. For example, the offset angle can be about 154°.This increased curvature at the distal dissecting tip 24 can allowgreater contact with the posterior maxilla 12 as the surgical tool 16 isadvanced toward the PPF 14.

The distal dissecting tip 24 also includes a leading edge 56, all oronly a portion of which may be blunt or sharpened. For example, theleading edge 56 can have a rounded or curved cross-sectional profilesimilar to the leading dissection edge of known periosteal elevators. Asshown in FIG. 8, the distal dissecting tip 24 can include a continuousleading edge 56. In this configuration, the continuous leading edge 56forms a semi-circular, arc-shaped, or crescent shape without anyinterruptions. The degree to which the leading edge 56 is arched can bevaried, for example, to impart the distal dissecting tip 24 with anoval-shaped configuration. As discussed above, the insertion groove 26of the surgical tool 16 is tapered such that the second depth at thedistal end 46 is less than the first depth at the proximal end 48 of theinsertion groove. Consequently, when the distal dissecting tip 24 isadvanced to the PPF 14, the distal dissecting tip must be elevatedslightly from the tangent bony surface to allow the tunneling member 44to be advanced into close proximity of the SPG 10.

Illustrated in FIG. 10 and FIGS. 13-17 is another aspect of the presentdisclosure comprising a surgical tool 58 configured to facilitatedelivery a neurostimulator 60 (FIG. 11) to a craniofacial region of asubject. A neurostimulator 60 capable of being delivered by the surgicaltool 58 can generally include any active implantable medical deviceconfigured to deliver electrical stimulation, alone or in combinationwith other types of stimulation to tissue of a subject. Theneurostimulator 60 can further include any active implantable medicaldevice configured for implantation for a relatively short period of time(e.g., to address acute medical conditions) or a relatively long periodof time (e.g., to address chronic medical conditions). Additionally, theneurostimulator 60 can include one or more elements used to record ormonitor a physiological response of a subject's tissue (e.g., adelivered therapy), as well as one or more other components thatinterface with the patient's tissue (e.g., therapeutic agent deliverymechanisms, sensors, etc.).

In one example of the present disclosure, the neurostimulator 60 can beconfigured as shown in FIG. 11 and disclosed in U.S. patent applicationSer. No. 12/765,712 (hereinafter, “the '712 application”), the entiretyof which is hereby incorporated by reference. Briefly, theneurostimulator 60 can comprise a stimulator body 62, an integralstimulation lead 64, which includes one or more stimulating electrodes66, and an integral fixation apparatus 68. The neurostimulator 60 can beimplanted as disclosed in the '712 application, i.e., such that thestimulator body 62 is positioned sub-periosteally medial to the zygoma70 on the posterior maxilla 12 within the buccal fat pad (not shown) ofthe cheek, and the integral fixation apparatus 68 is anchored to thezygomaticomaxillary buttress 72 such that the integral stimulation lead64 is placed within the PPF 14 or, more specifically, in very closeproximity to the SPG 10.

As described in more detail below, the neurostimulator 60 can bedeployed from the surgical tool 58 via a neurostimulator deliveryapparatus 74 (FIG. 12). The neurostimulator delivery apparatus 74includes an arcuate distal portion 76, a proximal handle portion 78, andan intermediate hub portion 80 that is integrally connected to each ofthe arcuate distal portion and the proximal handle portion. Theintermediate hub portion 80 is configured and shaped to snugly receive aportion of the stimulator body 62. The arcuate distal portion 76comprises a splittable sheath 82 that is securely affixed to a spine(not shown in detail).

The surgical tool 58 (FIG. 10) of the present disclosure is designed andconfigured to facilitate delivery a neurostimulator 60 in very closeproximity (e.g., about 1-5 mm) to the SPG 10 such that targetedelectrical stimulation or delivery of electrical current from theneurostimulator to the SPG can be accomplished. As shown in FIG. 13, thesurgical tool 58 comprises a handle portion 84, an elongate shaft 86that includes a contoured distal portion 88 having a flared distaldissecting tip 90, and an insertion groove 92 on the elongate shaft. Thesurgical tool 58 is designed and configured to be inserted trans-orallyfrom an incision located on the anterior maxilla 28.

The surgical tool 58 comprises a proximal portion 94, a contoured distalportion 88, and an intermediate portion 96 extending between theproximal portion and the distal portion. The proximal portion 94 and theintermediate portion 96 define a longitudinal plane P that extendsbetween the proximal and intermediate portions. The surgical tool 58 canhave a length L of about 10 cm to about 30 cm. For example, the surgicaltool 58 can have a length L of about 12 cm (e.g., 12.4 cm). The surgicaltool 58 can be made of a rigid or semi-rigid medical grade metal ormetal alloy, such as titanium or stainless steel, medical grade plastics(e.g., PEEK, polycarbonate, nylon), ceramics (e.g., aluminum, zirconiumoxide), combinations of metals, ceramics, plastics or plasticcomposites, and the like.

The proximal portion 94 of the surgical tool 58 can have a thicknessT_(p) of about 2 mm to about 4 mm (e.g., about 3 mm). The intermediateportion 96 can have a thickness that is similar or identical to thethickness T_(p) of the proximal portion 94. It will be appreciated,however, that the thickness of the intermediate portion 96 can decreaseas the intermediate portion tapers to the distal portion 88. As shown inFIG. 14, the proximal portion 94 includes an ergonomic handle 98 thatcollectively forms the handle portion 84 and is securely disposedthereon. The handle 98 can have a length of about 6 cm to about 12 cm,and vary in diameter from a proximal end 100 (e.g., about 0.5 cm toabout 3 cm) to a distal end 102 (e.g., about 0.5 cm to about 2 cm). Thehandle 98 can include various features to provide grip and tactilemaneuverability, such as circumferential ridges or a cross-hatchedprecut pattern into the material forming the handle. The handle 98 canbe made of a rigid or semi-rigid medical grade metal or metal alloy,such as stainless steel, medical grade plastics, polymers, and the like.

The distal portion 88 of the surgical tool 58 is shaped and configuredto allow a user to simply and accurately traverse the anteriorcraniofacial skeletal anatomy to reach the PPF 14. The distal portion 88is defined by oppositely disposed first and second major surfaces 104and 106, which collectively form an arcuate shape relative to thelongitudinal plane P. For example, the first major surface 104 of thedistal portion 88 has a concave shape relative to the longitudinal planeP. The distal portion 88 can have a thickness T_(d) of about 2 mm toabout 5 mm. The thickness T_(d) of the distal portion 88 can be uniformor, alternatively, the thickness T_(d) can decrease or taper at thedistal dissecting tip 90. The distal portion 88 can have a radius ofcurvature so that a user can maintain contact with the posterior maxilla12 while advancing the surgical tool 58 to the PPF 14. For example, thedistal portion 88 can have a radius of curvature of about 8 cm to about3 cm.

To prevent unwanted rotation of the surgical tool 58 during use, thedistal dissecting tip 90 can be offset from the longitudinal plane P. Asshown in FIG. 13, the entire distal dissecting tip 90 can be offset adistance D_(o) from the longitudinal plane P. The distance D_(o) can beabout 0.1 mm to about 5 mm. In one example of the present disclosure,the distance D_(o) can be about 3 mm (e.g., 3 mm).

The surgical tool 58 (FIG. 14) additionally includes an insertion groove92 on the elongate shaft 86 and, in particular, on the distal portion88. The insertion groove 92 is adapted, shaped, and configured tofacilitate precise, directional placement of a neurostimulator 60 withinor about the PPF 14. For example, the insertion groove 92 can be shapedand configured to slidably receive, support, and guide the spine of theneurostimulator delivery apparatus 74. As shown in FIG. 14, theinsertion groove 92 extends across the distal portion 88 of the surgicaltool 58 between the distal dissecting tip 90 and the intermediateportion 96. For example, the insertion groove 92 can extend across onlythe distal portion 88 of the surgical tool 58 and not the intermediateportion 96 and/or the proximal portion 94.

The insertion groove 92 can be embedded or recessed in the first majorsurface 104 of the distal portion 88. The particular dimensions of theinsertion groove 92 can vary depending upon the dimensions of surgicalguide 58 and/or the dimensions of the neurostimulator delivery apparatus74 (i.e., the spine). In one example of the present disclosure, theinsertion groove 92 can have a depth of between about 0.5 mm and about1.2 mm, a width W_(g) (FIG. 11) of between about 1 mm and about 2 mm(e.g., 1.6 mm), and a length L_(g) (FIG. 6B) of between about 2 cm andabout 8 cm (e.g., 6 cm). Although the insertion groove 92 is shown inFIG. 17 as having a semi-circular cross-sectional shape, it will beappreciated that the insertion groove can have other cross-sectionalshapes (e.g., square-shaped, V-shaped, etc.) to facilitate engagement ofthe surgical tool 58 with the neurostimulator delivery apparatus 74.

Referring to FIG. 15, the depth and width W_(g) of the insertion groove92 can remain uniform across the length L_(g) of the insertion groove tofacilitate engagement and release of the neurostimulator deliveryapparatus 74 to and from the surgical tool 58. For example, theinsertion groove 92 can have a depth that is the same or substantiallythe same across the length L_(g) of the insertion groove. That is, theproximal end 108 of the insertion groove 92 can include a first depththat is equal to or about equal to a second depth at the distal end 110of the insertion groove. Alternatively, the depth and width W_(g) of theinsertion groove 92 can vary across the length L_(g) of the insertiongroove. For example, the depth of the insertion groove 92 can taper fromthe distal end 110 of the insertion groove to the proximal end 108 ofthe insertion groove, where the insertion groove is no longer present asit reaches the discharge slot 118. In another example, the depth of theinsertion groove 92 at the proximal end 108 can gradually decreasetowards the distal end 110 of the distal dissecting tip 90 until theinsertion groove meets the discharge slot 118 and is thus no longerpresent.

The distal portion 88 of the surgical tool 58 can include a flareddistal dissecting tip 90. By “flared” it is meant that all or only aportion of the distal dissecting tip 90 is shaped and configured toextend away from the distal portion 88 of the elongated shaft 86 axiallyand/or distally, and typically also radially. The distal dissecting tip90 includes a length L_(t) that extends between a proximal end 112 and adistal end 114 thereof. The length L_(t) can be about 0.1 cm to about 1cm, such as about 0.5 cm (e.g., 0.25 cm). The distal dissecting tip 90also includes a width W_(t) that increases from the proximal end 112 tothe distal end 114 of the tip. The width W_(t) of the distal dissectingtip 90 is greater than the width W_(d) of the distal portion 88. In oneexample of the present disclosure, the width W_(t) at the distal end 114of the distal dissecting tip 90 can be about 2.5 mm to about 6 mm (e.g.,4.16 mm).

As described above with reference to FIG. 9, a first surface 54 of thedistal dissecting tip 24 and 90 extends at an offset angle A relative tothe first major surface 40 and 104 of the distal portion 22 and 88(respectively). For example, all or only a portion of the distaldissecting tip 90 can have an increased curvature in the same plane asthe distal portion curvature of the surgical tool 58. The offset angle Acan be less than 180°. For example, the offset angle can be about 154°.This increased curvature at the distal dissecting tip 90 can allowgreater contact with the posterior maxilla 12 as the surgical tool 58 isadvanced toward the PPF 14. In addition, the offset angle A may beconfigured or dimensioned to add thickness to the surgical tool 58 andthereby prevent the sharp leading edge 56 from entering the PPF 14 anddamaging the SPG 10 or other soft tissue structure(s) (e.g., othernerves, blood vessels, etc.).

The distal dissecting tip 90 also includes a leading edge 116, all oronly a portion of which may be blunt or sharpened. As shown in FIGS.16-17, the distal dissecting tip 90 has a bifurcated configuration suchthat the leading edge 116 is interrupted and a discharge slot 118 isformed within the distal dissecting tip. When the distal dissecting tip90 is inserted into or about the PPF 14 (e.g., at the opening of thePPF), the discharge slot 118 allows the stimulation lead 64 of theneurostimulator 60 to be inserted into the PPF without removing orelevating the distal dissecting tip from the tangent bony surface.

The discharge slot 118 includes a width W_(s) and a length L_(s). Thewidth W_(s) of the discharge slot 118 can be less than the width W_(t)of the distal dissecting tip 90. In one example of the presentdisclosure, the width W_(s) of the discharge slot 118 can equal, or beabout equal to, the width W_(g) of the insertion groove 92, which can beconfigured and dimensioned to accept the stimulation lead 64 of theneurostimulator 60. The length L_(s) of the discharge slot 118 can beless than the length L_(t) of the distal dissecting tip 90 (FIGS. 16-17)or, alternatively, the length L_(s) of the discharge slot can be aboutequal to the length L_(t) of the distal dissecting tip (FIG. 15).Additionally, the length L_(t) of the distal dissecting tip 90 in FIGS.14-15 can be less than the length L_(t) of the distal dissecting tip inFIGS. 16-17. The discharge slot 118 can have an elongated, U-shapedconfiguration (FIG. 15), a V-shaped configuration (FIGS. 16-17), or anyother desired configuration.

Illustrated in FIG. 18 is another aspect of the present disclosureincluding a method 120 for delivering a neurostimulator 60 to withinclose proximity of a SPG 10. At Step 122 of the method 120, an incision130 (FIG. 19) is made at a gingival-buccal insertion site. The incision130 can be made in a similar or identical manner as disclosed in U.S.Patent Publication No. 2010/0185258 A1 to Papay, which is herebyincorporated by reference in its entirety. Briefly, for example, a #10scalpel blade (not shown) can be used to make an incision 130 in asuperior-inferior manner between the second and third molars 132 and134.

At Step 124, the surgical tool 16 shown in FIGS. 2A-B (referred to belowas “the first surgical tool”) in then inserted into the incision 130 asshown in FIG. 20. Prior to inserting the first surgical tool 16,however, the surgical anatomy of the subject is determined using one ormore imaging techniques (e.g., MRI, CT, ultrasound, X-ray, fluoroscopy,or combinations thereof). In particular, the anatomy of the subject'sskull, including the location and size of the PPF 14 can be determinedprior to insertion of the first surgical tool 16.

After inserting the first surgical tool 16 into the incision 130, thefirst surgical tool is urged in a posterior direction so that the firstmajor surface 40 of the distal portion 22 traverses under the zygomaticbone 70 along the maxillary tuberosity 136. The first surgical tool 16is then advanced further until the distal dissecting tip 24 engages thejunction formed by the posterior maxillary buttress 72 and the pterygoidplate 138, just inferior and lateral to the PPF 14. Advancement of thefirst surgical tool 16 may naturally stop when the distal dissecting tip24 is correctly positioned at the junction formed by the posteriormaxillary buttress 72 and the pterygoid plate 138.

At this point, the first surgical tool 16 is rotated in a superiordirection until the distal dissecting tip 24 is within (or nearlywithin) the PPF 14 (FIG. 21). This can be done by carefully “walking”the distal dissecting tip 24 up the pterygoid plate 138 until the distaldissecting tip (or other desired portion of the distal portion 22)slides into the PPF 14. At Step 126, advancement and positioning of thefirst surgical tool 16 from the incision to the PPF 14 forms a surgicalaccess cavity 140 (FIG. 22). As can be more clearly seen in FIG. 22, thesurgical access cavity 140 is shaped like a tunnel or trough thatextends from an open end 142 of the incision 130 to the PPF 14. Thefirst surgical tool 16 can then be removed to expose the surgical accesscavity 140.

Next, the surgical tool 58 (referenced to below as “the second surgicaltool”) is inserted into the surgical access cavity 140 as shown in FIG.23. After the second surgical tool 58 is appropriately positioned in thesurgical access cavity 140, an electrode lead blank 44 is carefullyinserted into the insertion groove 92 of the second surgical tool 58 andthen progressively advanced along the insertion groove. The electrodelead blank 44 can be configured to have the same or substantially thesame dimensions as the stimulation lead 64 of the neurostimulator 60.Although not shown in detail, the electrode lead blank 44 can comprisean elongated, flexible wire-like structure having a distal endconfigured to bluntly dissect tissue. The electrode lead blank 44 isurged along the insertion groove 92 until the distal end of theelectrode lead blank extends from the surgical access cavity 140 intoclose proximity with the SPG 10.

It will be appreciated that the second surgical tool 58 can beconfigured with the distal dissecting tip 90 shown in FIGS. 14-15 orFIGS. 16-17 depending, for example, on the craniofacial anatomy of thesubject. For example, it may be preferable to use a second surgical tool58 configured with the distal dissecting tip 90 shown in FIGS. 14-15 ininstances where the PPF 14 of a subject having a pterygomaxillaryfissure with a large width (e.g., greater than 3 mm). In such instances,the longer distal dissecting tip 90 shown in FIGS. 14-15 (as compared tothe distal dissecting tip in FIGS. 16-17) permits easier access to theposterior portion of the PPF 14. In other instances, it may bepreferable to use the distal dissecting tip 90 shown in FIGS. 16-17 fornarrower anatomic fissures, e.g., less than 3 mm due to the shorter tiplength (as compared to the distal dissecting tip in FIGS. 14-15).

As shown in FIG. 24, the electrode lead blank 44 is then removed fromthe subject. Next, the neurostimulator deployment apparatus 74 is matedwith the second surgical tool 58 (FIG. 25). For example, the spine ofthe neurostimulator deployment apparatus 74 can slidably engage theinsertion groove 92 of the second surgical tool 58. Once theneurostimulator deployment device 74 is properly mated with the secondsurgical tool 58, the neurostimulator 60 is deployed from theneurostimulator deployment apparatus (Step 129). The neurostimulator 60can then be implanted within the subject as discussed above anddisclosed in the '712 application. With the neurostimulator 60 securelyimplanted within the subject, an electrical current from theneurostimulator can be applied to the SPG 10 to treat a medicalcondition (e.g., headache). Advantageously, use of the electrode leadblank 44 with the second surgical tool 58 provides a pathway to the PFF14 (and thus the SPG 10) that can be accurately followed by thestimulation lead 64 as there is no need to remove or adjust the positionof the second surgical tool prior to implantation of the neurostimulator60.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications. Suchimprovements, changes, and modifications are within the skill of the artand are intended to be covered by the appended claims.

1. A surgical tool configured to provide surgical access to acraniofacial region of a subject, said surgical tool comprising: ahandle portion; an elongate shaft comprising a contoured distal portion,said distal portion shaped and configured to maintain contact with aposterior maxilla and elevate a periosteum off of the posterior maxillato avoid soft tissue dissection, said distal portion including a distaldissecting tip; and an insertion groove on said elongate shaftconfigured to receive, support, and guide a tunneling member.
 2. Thesurgical tool of claim 1, wherein said distal dissecting tip has aflared configuration.
 3. The surgical tool of claim 1, wherein saidhandle portion further comprises a proximal portion and an intermediateportion that extends between said proximal and distal portions, saidproximal and intermediate portions defining a longitudinal plane thatextends therebetween, said distal portion having an arcuateconfiguration relative to said longitudinal plane.
 4. The surgical toolof claim 3, wherein said insertion groove is recessed into said elongateshaft.
 5. The surgical tool of claim 1, wherein said insertion groovetapers from a distal end of said insertion groove to a proximal end ofsaid insertion groove, said insertion groove having a first depth atsaid proximal end that is greater than a second depth at said distalend.
 6. The surgical tool of claim 4, wherein said insertion groove islocated on an opposing edge of said elongate shaft.
 7. The surgical toolof claim 1, wherein said distal dissecting tip includes a continuousleading edge.
 8. The surgical tool of claim 1, wherein a first surfaceof said distal dissecting tip extends at an offset angle relative to afirst surface of said distal portion.
 9. The surgical tool of claim 8,wherein said offset angle is less than 180°.
 10. The surgical tool ofclaim 1, wherein a portion of said distal dissecting tip is collinearwith said longitudinal plane.
 11. The surgical tool of claim 1, whereinsaid tunneling member comprises an electrode lead blank.
 12. A surgicaltool configured to facilitate delivery a neurostimulator to acraniofacial region of a subject, said surgical tool comprising: ahandle portion; an elongate shaft comprising a contoured distal portion,said distal portion shaped and configured to be advanced under azygomatic bone along a maxillary tuberosity towards a PPF, said distalportion including a distal dissecting tip; and an insertion groove onsaid elongate shaft configured to receive, support, and guide aneurostimulator deployment apparatus.
 13. The surgical tool of claim 12,wherein said distal dissecting tip has a flared configuration.
 14. Thesurgical tool of claim 12, wherein said handle portion further comprisesa proximal portion and an intermediate portion that extends between saidproximal and distal portions, said proximal and intermediate portionsdefining a longitudinal plane that extends therebetween, said distalportion having an arcuate configuration relative to said longitudinalplane.
 15. The surgical tool of claim 12, wherein said insertion grooveis recessed into said elongate shaft.
 16. The surgical tool of claim 12,wherein said insertion groove is located on an opposing edge of saidelongate shaft.
 17. The surgical tool of claim 12, wherein said distaldissecting tip has a bifurcated configuration.
 18. The surgical tool ofclaim 12, wherein said insertion groove has a depth that issubstantially the same between a proximal end and a distal end of saidinsertion groove.
 19. The surgical tool of claim 12, wherein a firstsurface of said distal dissecting tip extends at an offset anglerelative to a first surface of said distal portion.
 20. The surgicaltool of claim 19, wherein said offset angle is less than 180°.
 21. Thesurgical tool of claim 12, wherein said distal dissecting tip is offsetrelative to said longitudinal plane.
 22. A method for delivering aneurostimulator to within close proximity of a sphenopalatine ganglion(SPG), said method comprising the steps of: making an incision at agingival-buccal insertion site; inserting a first surgical tool into theincision; advancing the first surgical tool under a zygomatic bone alonga maxillary tuberosity towards a PPF to form a first surgical accesscavity; forming a second surgical access cavity at an end of the firstsurgical access cavity that is in close proximity to the SPG; anddelivering the neurostimulator in close proximity to the SPG via thefirst and second surgical access cavities.
 23. The method of claim 22,wherein said advancing step further comprises the steps of: advancingthe first surgical tool until a distal dissecting tip of the firstsurgical tool engages a junction formed by a posterior maxillarybuttress and a pterygoid plate; and rotating the first surgical tool ina superior direction until the distal dissecting tip is positioned aboutthe PPF.
 24. The method of claim 22, wherein said step of forming asecond surgical access cavity further comprises the steps of: advancinga tunneling member into contact with an insertion groove of the firstsurgical tool; urging the tunneling member along the insertion grooveinto contact with an end of the first surgical access cavity; andadvancing the tunneling member through the end of the first surgicalaccess cavity to form the second surgical access cavity.
 25. The methodof claim 22, wherein said step of delivering the neurostimulatorincludes the further steps of: withdrawing the first surgical tool andthe tunneling member from the first and second surgical access cavities,respectively; securely mating the neurostimulator with a neurostimulatordelivery device, the neurostimulator including a stimulation lead andthe neurostimulator delivery device including a spine; advancing asecond surgical tool into the first surgical access cavity; slidablyengaging the spine with an insertion groove of the second surgical tooluntil the stimulation lead is positioned within the second surgicalaccess cavity; disengaging the neurostimulator from the neurostimulatordeployment apparatus; and securing the neurostimulator about the PPF sothat the stimulation lead is in close proximity to the SPG.
 26. Themethod of claim 22, further comprising the step of applying anelectrical current from the neurostimulator to the SPG to treat amedical condition.
 27. The method of claim 26, wherein the medicalcondition is pain.
 28. The method of claim 27, wherein the pain is atleast one of headache and facial pain.